1. Field of the Invention
The present invention relates to a variable attenuator for use in optical fiber communication and optical network technology, and particularly to a variable attenuator with an adjusting mechanism controllable from two different locations on the variable attenuator.
2. Description of Related Art
A fiber optic attenuator is a passive optical component for reducing optical power propagating in a fiber, and may perform fixed or variable attenuation. Optical attenuators are widely used in optical transmission systems and optical networks.
A variable attenuator generally has an optical filter. The filter has an effective filtering region disposed in the optical path between a collimator and a reflector. The filter has a filter density which increases from a lower density region to a higher density region. The transmitted light is attenuated to different intensities by linear movement of the filter.
One prior art variable optical attenuator features a rotateable screw rod as the attenuation adjusting mechanism. The screw rod is threadedly engaged with a carrier, and a variable density filter is mounted on top of the carrier. The carrier (and filter) moves from side to side, the filter being in the path of the light beam. The direction of movement of the carrier and filter depends on the direction of rotation of the screw rod. The screw rod of this prior art optical attenuator has an operating surface at only one side of the attenuator. Therefore, the adjusting mechanism of this attenuator is operable at only one location on the side of the attenuator. Use of this attenuator, therefore, is limited to locations where enough space exists on the side of the attenuator where the adjusting mechanism is adjusted.
An improved optical attenuator having an adjusting mechanism which allows operation from two different locations on the attenuator is desired.
An object of the present invention is to provide an improved variable attenuator having an adjusting mechanism which is operable from at least two adjusting locations on the attenuator.
Another object of the present invention is to provide an improved variable attenuator that can be used in a larger number of circumstances.
The present invention is a variable optical attenuator having an adjusting mechanism operable from two opposite sides of the variable attenuator. Specifically, the variable optical attenuator comprises a housing, an optical module, a reciprocating means, and a filter.
The housing has an inner cavity. A pair of side holes penetrates the housing at each side of the inner cavity and provides communication between the inner cavity and two outer sides of the housing.
The optical module comprises a frame, a reflector and a collimator. The frame has a groove with an inner wall, and a through hole communicating with the groove. The reflector is fixed on the inner wall of the frame and is disposed coaxially with the through hole. The collimator is positioned in the through hole and fixes ends of an input optical fiber for carrying transmission optical signals to the attenuator and an output optical fiber for receiving the resulting attenuated transmission optical signals from the attenuator.
The reciprocating means comprises a carrier and a screw rod. The screw rod has a screw portion at its middle and a pair of gripping portions at either end of the screw portion. An operating surface in the form of a slot is located at each end of the screw rod.
When assembled, the two ends of the screw rod fit into and are accessible at the side holes at either side of the housing, and the carrier is movable within the inner cavity and engages with the screw rod. The filter fits on the carrier and is positioned between the collimator and the reflector. The carrier moves lengthwise along the screw rod when the screw rod is rotated. The filter moves along with the carrier. Since the screw rod has operating surfaces on each of its ends, the adjusting mechanism of the variable attenuator is operable from two opposite sides of the housing.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.